1. Field of the Invention
This invention relates to watercraft, especially jet-powered personal watercraft (“PWC”). More specifically, the invention concerns power sources used in watercraft, such as PWCs.
2. Description of Related Art
Jet powered watercraft have become very popular in recent years for recreational use and for use as transportation in coastal communities. The jet, power offers high performance, which improves acceleration, handling and shallow water operation. Accordingly, jet-powered PWCs and sport boats have become common place, especially in resort areas.
PWCs are typically powered by a two or four stroke internal combustion engine (ICE) that has a drive shaft operatively connected to the jet pump. While such engines provide ample power for PWCs, they create both environmental and noise pollution. Furthermore, the idle speed of a conventional ICE is generally well above 1000 rpm. Unfortunately, when PWCs are operated at low speeds such as during trolling or operating in and around people, obstacles, docks, etc., it is preferred to have an engine speed (and proportionally corresponding PWC speed) of less than 1000 rpm. The precise locations in which riders use PWCS at low speeds (i.e., around docks, people, shore, etc.) are also the locations where preventing noise and environmental pollution is most important. Farther away from docks, people, and shore, riders tend to drive PWCs faster and increased power is highly desirable.
During an internal combustion engine's slow start routine, the majority of hydrocarbons are emitted. It would be desirable, therefore, to provide additional power to the power train until the engine is fully engaged. One way to provide additional power is to use stored electrical energy. However, conventional electrical systems are 12-14V (volt), which have a low limit of how much total vehicle power and amount can be supplied, particularly in view of current standard electrical peripherals. Such 12-14 V systems also require bulky wiring harnesses and electronics that experience voltage sags and spikes.
One way this problem has been addressed is to update the electrical system to a 42 V standard. A 42 V standard architecture will enable the addition of technologies that would improve fuel economy, such as start/stop strategies and torque boosters, decrease the weight of the overall wiring, and allow the use of advanced solid state circuitry that facilitates advanced technology.
A need has developed for a watercraft that can alternately operate at low speeds while minimizing noise and environmental pollution and at higher speeds where increased power is desired.
In the field of land-driven wheeled vehicles such as automobiles, one way environmental concerns have been addressed is to provide a “hybrid” vehicle, which uses a hybrid gas/electric power system. For example, an article entitled “High Bred Hybrids” in the March 2001 issue of Popular Science, which is hereby incorporated herein by reference, describes the simultaneous and/or alternating use of engines and electric motors to power automobiles.
In conventional watercraft with jet propulsion systems, the engine's crankshaft is permanently rotationally coupled to the impeller of the jet propulsion unit. Accordingly, even when the engine is idling and the operator is not actuating the throttle, the impeller rotates. Consequently, even when the operator does not intend to have the watercraft move, the jet propulsion unit creates at least some thrust. Similarly, to start the engine, a starter motor must simultaneously start the engine and drive the propulsion system.
In waterways near docks, inlets, etc., it is common to have low maximum speed limits for watercraft. To ensure that an operator's watercraft does not exceed such speed limits, the watercraft operator must currently continuously monitor the watercraft's gauges while simultaneously maneuvering the watercraft within such obstacle-laden waterways.